System for eliminating interference



Mapch 16 1926, A 1,576,667

' J. o. MAUBORGNE ET AL SYSTEM FOR ELIMINATING INTERFERENCE Filed Feb. 9, l1924 Patented Mar, 16, 1926.

UNITED STATES PATENT OFFICE.

JOSEPH O. MAUBORGNE AND GUY HILL, OF WASHINGTON, DISTRICT OF COLUMBIA.

SYSTEM FOR ELIMINATING INTERFERENCE.

Application filed February 9, 1924. Serial No. 691,559.

To all who/1t 'it muy conce/11n.'

Be it known that we, JOSEPH O. MAU- BoneNn and GUY HILL, citizens of the United States, residing at lvashington, District of Columbia, have invented certain 'new and useful Improvements in Systems for Eliminating Interference, of which the following is a specification.

This invention relates to the art of eliminating undesired frequencies in radio receiving circuits and discloses a new and useful system for accomplishing this purpose.

In ourcopending applications Serial Nos. 383,720, 459,530, 81,3% and 401,746, we have 'described the construction and use of a coil which we designated as a resonance Wave coil for use as an antenna or collector of high frequency energy in connection with receiving apparatus.

We have found that the same type of wave coil may be employed to absorb energy from a lead connected to the receiving circuit to such a marked degree that if the wave coil be adjusted to any given frequency which is undesired, the energy of this frequency will be eliminated by the wave coil, so that the receiving apparatus will be substantially free from the undesired frequency. In other words, this wave coil, when properly connected, has been found to accomplish the same purpose as the so-called Wave trap.

It is characteristic of the apparatus we propose that it is extremely simple Vin operation as the inductance and capacity of the wave coil, or open circuit wave trap-in the simplest form of our apparatus remain fixed, and elimination of the undersized frequency is accomplished solely by moving a single variabler electrical connection along the wave coil until the undesired signals are reduced to a minimum, the single lead making variable connection to the coil be ing connected to the same point of the circuit from which undesired signals are to be eliminated. This is an improvement over existing wave trap circuits which consist of lumped inductances and capacities either or both being variable and in the form of a closed circuit.

It is a further characteristic of our invention that a plurality of such coils may be employed, and so connected to a single circuit as to simultaneously eliminate two or more undesired frequencies, the arrangement becoming an electric filter permitting band tuning if a suliicient number of coils and proper arrangement thereof be made.

A resonance wave coil, suitable for the purpose of this invention, consists, in one of its forms, of a coil preferably uniformly wound with wire to form of a helix, in the form of an open circuit, having fixed distributed inductance and capacity of such values that the coil will respond to a wide range of frequencies. The coil is provided with a single adjustable electrical connection so that connection can be made to any desired element of the wave coil. Instead, of a variable connection to the coil, this connection can be fixed or connections be made to taps and fine or Vernier adjustment made by means of an adjustable metallic extension electrically connected to one or both ends of the coil.

In our copending applications, referred to above, more detailed information has been given concerning the construction and characteristics of these coils.

Our invention will be best understood by reference to the followingr description taken in connection with the accompanying drawings in which f Fig. l is a diagrammatic view of one form of the device used for the Velimination of high frequencies.

Figure 2 is a diagrammatic view showing the open circuit wave trap connected in j a normal way to an ordinary radio receiving system. l

yFigure 3 is a diagramma-tic view showing the method of connecting our device to an ungrounded loop receiving apparatus.

Figure I is a diagrammatic view, similar to Figure 3, except that the receiving apparatus is grounded, and the wave trapvis connected to the ground lead. l

Figure 5 is a diagrammatic View showing twoconductors connected to the same re ceiving apparatus, an open circuit wave trap being connected to each of the conducto-rs.

Figure 6 is a diagrammatic view, similar to Figure 2, except that a plurality of wave trapsis connected to the same conductor.

Figure 7 shows details of construction of the form of wave coil indicated diagrammatically in all of the preceding ligures.

Referring more particularly to the drawings, Tl represents a conductor through which high frequency currents pat-'s to a receiving apparatus, which is connected to the conductor l. 3 represents a. Wave coil and 4 a single lead connecting electrically the wave coil to t-he conductor l at point 5. 6 is a slider electrically connected to lead Li, so that the conductor l, by means of lead Ll, can be connected to any desired point on the -Wave coil. 7 is a small metallic e:;tension electrically connected to one end of the Wave coil 3. The length of the extension can be varied by operation of the knob 8, for the purpose of varying the constants of the coil, and operates as a vernier affording a means: of accurate timing.

lVe have found that if, in the conductor l, there are flowing two currents of different Jfrequencies that by means of the apparatus shown, one of these frequencies can be received and the other eliminated. rlhus the undesired `frequency Will not cause any appreciable elfect to be produced in the receiving apparatus.

Several methods of procedure can be carried out in order to eliminate the undesired frequency. The methods Will vary in details depending upon actual conditions. lf the Wave coil has been calibrated and the Wave length of the interfering signal is known, the ivave coil should bel connected to the conductor l, and slider 6 moved to the position that lWill bring the Wave coil in tune with the interfering frequency. rIhe receiving apparatus 2 should then be tuned in the ordinary manner and it Will be found that litt-le or no interference Will be present, depending upon the percentage of separation o-f the tivo frequencies. A slight retuningl of the wave coil and also of the receiving apparatus Will at times produce further reduction of the interfering signal.

If the Wave length of t-he interfering signal is not known, or the. Wave coil has not been calibrated, the following procedure should he used. The receiving set should be tuned to the desired frequency ivitli the Wave coil disconnected from conductor l. Then the Wave coil should be connected' to the conductor l at pointI 5 and the slide-r G moved until the interfering signal vanishes or is reduced to a minimum. In some cases, retuning of receiving apparatus will be. found necessary after connecting Wave coil 3 and lead flto conductor l.

ln both of the methods described, linal exact timing of the Wave coil may be made by adjusting the length of the metallic eX- tension 7, which acts as a Vernier. lli/Then extension 7 is used for enact timing, the slider 6 does not need to be adjusted as accurately as when ivave coil 3 is not provided with the extension described.

Instead of having a. slider, such as G, which can make contact With each and every Lames? turn of the coil, a series of taps may be brought out from the coil, to any one of which lead Zl can be connected, to provide approximate tuning, the exact tuning being finally accomplished by varying the e.;tension 7. Extension 7 is not an essential part of the open circuit wave trap described but may be added for convenience in obtaining exact timing. i

Figure 2 is similar to Figure l. ln this figure the. conductor l is a lead connecting antenna A to receiving set 2. Receiving 2 is connected to ground G by means of lead l, if desired, altho it is to be noted that the Wave coil 3 Will function as a rave trap Whether receiving apparatus 2 he grounded or not.

Symbols 3 to 8 represent similar apparatus to that indicated by the same symbols in Figure l and perform the same functions as described in the specification pertaining to that figure.

rlhe operation of the apparatus for eliminating a single interfering frequency is identical with that described for Figure l. ce

Figure 3 shows the method of connecti 35 the open circuit Wave trap to a loop antenna and associated receiving apparatus. i is. in this case, the conductor forming part of the circuit of the loop antenna. 2 represents c? the receiving appa atus Which combines ivith coil l to form an ordinary loop rcceivcr, which is Well knoavn in the art. l() and il are the terminals of the receiving apparatus to Which the loop l is connected. in receiving sets Where one terminal of the loop is connected to the grid of a vacuum tube, this terminal in thel ligure is represented by l0. lVehave found that it is pre e"- able to connect lead Ll from Wave coil 3 to a point 5 as near as practicable to or coincident with, terminal 10 which We have designated as the grid terminal of the receiving apparatus 2.

Symbols and 1li to 8 inclusive represent similar apparatus to that indicated by the same symbols in Figure l, and perform the same functions as described in the specification pertaining to that ligure.

The operation of the apparatus for eliminating a single interfering 'frequency is identical ivith that described for Figure l.

Fig. represents a grounded loop recciing circuit. l represents a lead coi l' terminal l2 of loop receiving an lo ground. rTerminal l2 is ordin; trically connected With the file Where a vacuun'i tube dote. vWhere a loop receiving set connec-f 'i ground as shown in this ligure. in cases, an increase in signal e rl but considerable interference mai.' be E llfl .duced through the ground lead lf ll. 'nare found that by connecting the open circuit Wave trap herein described to a point i; on im) said ground lead 1', that the effect of the interfering frequency on the receiving apparatus 2 can be eliminated.

Symbols 1 to l inclusive and G to 11 inclusive represent similar apparatus to that indicated by the same symbols in Fig. 3, and perform the same functions as described in the specification pertaining to that figure and to Figure 1.

The operation of the apparatus for el init nating a single interfering frequency is identical with that described for Figure 1.

Figure represents two conductors 1 and 1 such as a pair of wiresthat might be used in line radio, wired Wireless, or carrier current telegraphy or telephony, said couductors supplying the high frequency current to suitable receiving apparatus 2. ln

' case it is desired to eliminate a single interfering frequency which mifrht be present on each of said conductors 1 and 1, tvvo open circuit Wave traps are used, one connected to each of the conductors 1 and 1 respective ly as shown in the figure, Where 3 and S represent similar Wave coils, and the other symbols as 7 and 7 represent similar details of the similar apparatus. 125 and 14 are the terminals of the receiving apparatus 2, connected to conductors 1 and 1 respectively.

Symbols 3 to 8 inclusive and the corresponding symbols 3 to 8 inclusive represent apparatus similar to that indicated by the same symbols in Figure 1 and perform the same functions as described in the specilication pertaining to Figure 1'.

The operation of the apparatus for eliminat-ing a single interfering frequency ccnsists in adjusting each of the tivo open circuit Wave traps as described for a single Wave trap in specification referring to Figure 1.

Figure 6 represents the use of a Vplurality of Wave'co-ils 3, 3 and 8 all connected to a conductor 1 through which high frequency currents pass to receiving apparatus 2, for the purpose of eliminating` a'plurality of interfering frequencies.

The symbols used for the respective Wave coils correspond With each other and with those used in Figure 1, and the apparatus is similar to and performs the same functions as described in the specification pertaining to Figure 1, except that a plurality of frequencies can be eliminated by the arrangement shown in Figure Gf The operation of the apparatus for eliminating a plurality of interfering frequencies consists in separately adjust-ing each. of the open circuit Wave traps to eliminate one of the interfering frequencies as described Afor a single Wave trap in the specification relative to Figure 1.

Referring specifically to Figure (l, in case there are only two interfering frequencies,

and one of these is very powerful, two of the Wave traps shown may be4 adjusted to lthe same frequency-that of the strong interfering signal, While a third may be adj usted to eliminate the weaker frequency.

Figure 7 shows details of construction of the Wave coil shown in Figuresl to 6 inclusive. 3 represents the Winding of the coil proper, a section of which is shown as removed to permit explanation of internal 7 resents a metal case in which strip 7 coils up 8 under action of spring not shown in ydrawing which is connected at 'point 2a to end of strip 7 and the other end of said spring is connected electrically and mechanically to case 23, which as before stated is in elec trical connection With coil 3 at point 22. Strip 7 at its outer end is connected to the tip of an insulating rod, 2G, Which passes through a guide 27' in the end of rod 2G,

shown as point 28 in the figure, is attached 9 to an endless cord 29 on pulleys 30 and 31 which have their shafts turning in bearings Which are permanently fixed to core, 21.' Pulley 30 has its movable shaft extended through core Q11 terminating in knob 8.

By turning knob 8, string 9 is made to extend or Withdraw roc 25 from core 21, thereby causingvmetallic strip 7 to extend, or coil up within case 28, thereby permitting continuous fine adjustment of the constants of the coil.

l/Vhile the above details show a formof coil which We have found satisfactory in op eration, various other modifications and variations of the device could be employed l which would function in a similar manner.

lllhile in the foregoing drawings and specifications ive have indicated only one physical form ofan open circuit Wave trap, We do not confine ourselves to the use of a wave coil cf the particular forni indicated. ln fact, Ware coils of other forn'is, sonic of which are indicated in our ccpending apn plications hereinbefore referred to might be einploycd.V Similarly While We have indicated inthe specifications and drawings herewith that each of the Wave coils is provided with a variable metal extension, as before stated, this extension is an aid in sharp tuning but is not absolutely necessary for successfully 'carrying out of our invention. Also, while in the drawing and specific-atiens herewith We have shown the open circuit Wave trap connected to certain specific elements of circuits We do not limit ourselves to the exact arrangements shown, as, due to complicated and various types of receiving circuits it might be desirable to attach our forni of wave trap to other elements than those which We have indicated.

Vhile we have found that Wave coils constructed and utilized as wave trapsA as shown and described in the accompanying figures and drawings have functioned in an entirely satisfactory manner, we have also obtained satisfactory operation by having` the Wave coil enclosed in a metal case or shield, such shielding in certain cases being used to prevent interaction between adjacent coils er betivecn coils and rece'ving apparatus. We have not shown such shields in the above iigures as we consider them a refinement not essential for the successful operation of our invention.

Thilo for the salte of simplicity in the majority of the figures We have shown only one Wave trap, it is to be understood that any desired number of traps can be used in any of the combinations as shown diagran matically in Figure 6.

Having thus described our invention, We claim:

l. A system for eliminatingl undesired high frequencies in receiving systems, comprising a conductor carrying tivo different frequencies, means for receiving signals corresponding to the desired one of these frequencies, an open circuit u'ave trap in the form of a resonance Wave coil having distributed inductance and capacity, said Wave coil being connected by a single lead, said conductor larrying high frequency energy to the recei vving apparatus, means for selecting the element of the Wave coil to which said single lead is to be attached so that said ivave coil will eliminate the effect of the undesired frequency upon the receiving` apparatus.

Q. A system for eliminating undesired high frequencies in receiving systems, comprising a conductor carrying tivo different frequencies, means for receiving signals corresponding to the desired one of these frequencies, an open circuit Wave trap in the form of a resonance Wave coil having distributed inductance and capacity, said u'ave coil being connected by a single lead, said conductor crrrying high frequency energy to the receiving apparatus, means for selecting the element of the u" ve. coil to which said single lead is to be attached, and means for varying the constants of the coil so that said Wave coil will eliminate the elliect of the undesired frequency upon the receiving apparatus.

3. A system for eliminating undesired high frequencies in receiving systems, comprising a conductor carrying two different frequencies, means for receiving signals corresponding` to the desired one of these frequencies, an open circuit wave trap in the form of a resonance Wave coil having distributed inductance and capacity, said Wave coil being connected by a single lead, said conductor carrying high frequency energy to the receiving apparatus, means for selecting the element of the wave coil to which sait. single lead is to be attached, and means for varying the constants of the coil so that said ivave coil will eliminate the effect of the undesired frequency upon the receiving apparatus, said means comprising an extensible metallic body electrically connccted to one'end of said Wave coil, and means for varying the effective electrical dimensions of said metallic body.

et. In an apparatus for eliminating undesired high frequencies in receiving systenis, a Wave coil consisting of an insulating tube, a single layer Winding of insulated ivire in the form of a helix Wound thereon, said Wire being nninsulated in part to permit contact to be made therewith by a slider provided with a terminal for connecting said coil to the remainder of the receiving apparatus, an extensible strip of metal electrically connected to one end of said coil, and means for ceiling and extending said strip of metal in prolongation of said Wave coil.

5. A system. for the reception of radio signals comprising in combination an antenna circuit, a receiving circuit coupled With said antenna circuit, a resonance Wave coil, and an independent connection from the said antenna to a point on said resonance Wave coil, said connection on said wave coil being adjustable.

6. A system for the reception of radio signals comprising in combination a ivire system over which high frequency signals are received, a receiving circuit coupled with said Wire system, a resonance Wave coil, and an independent connection from the said Wire system to a point on said resonance Wave coil said connection on said wave coil being' adjustable.

7. A system for the reception of radio signals comprising in combination an antenna circuit, a receiving circuit coupled with said antenna circuit, a resonance Wave coil, said resonance wave coil consisting of a conductor having distributed inductauce and capacity on which standing Waves are developed, and an independent connection from said antenna to a point on said resonance Wave coil, said connection on said wave coil being adjustable.

8. A .system for the reception of radio signals comprising an antenna circuit, a receiving circuit coupled with said antenna circuit, a resonance Wave coil having means whereby it may be brought into resonance for the frequency of t-he undesired interfering signal for absorbing the energy of the undesired signal, and an independent connection from the said antenna to a pointV on said resonance Wave boil, .said connection on said Wave coil being adjustable.

9. A system for the reception of radio signals comprising an antenna circuit, a receiving circuit coupled with said antenna circuit, a resonance Wave coil, and a separate connection from said antenna to a point on said resonance Wave coil, .said separate connection being adjusted so that said Wave coil operates as a Wave trap for a partieular signal frequency which it is desired excluded from the receiving system.

10. A system for the reception of radio signals comprising an antenna circuit, a receiving circuit coupled With said antenna circuit, a plurality of resonance Wave coils, separate connections independent one from the other between said antenna to points on each of said resonance Wave'ooils, each of said connections being independently adjustable whereby eaeh of said resonance Wave coils serves to absorb the energy of a separate signalling frequency.V

In testimony whereof We affix our signatures.

JOSEPH O. MAUBORGNE. GUY HILL.` 

